At the start of the film Kong hears what appears to be the roars of another Titan simian and follows it in hopes of finding a surviving member of his kind, only to find that the noises came from an Titan frog, much to his disappointment.
Kongs state in general at the beginning of the film. He’s found a home in Hollow Earth and is living a relatively good life all things considered but he still understandably lonely.
Illene Andrews: He’s the last of his kind and everyday he searches for a family he’ll never find.
Kong returns to Jia and the others with Suko by his side heavily injured from the battle with Skar King and Shimo. As he collapses from probably a combination of exhaustion and his injuries he tells Jia in sign language “I lost home.”
When Kong first meets the slaves, one of them drops the stone he was supposed to carry due to it being too heavy. Despite this accident being fairly inconsequential (nothing was damaged, nobody was hurt), he can be seen gasping in shock at this, because he already knows that he's going to be beaten for it regardless.
When Kong extends a hand to help the prisoner up, he hesitates at first, glancing at Kong's hand and not sure of what to do. You can tell that he's having difficulty comprehending the idea that someone is showing kindness to him in the sea of brutality he's had to endure. Becomes a happy tearjerker by the end of the movie, since the very same ape stands to witness Kong liberating the prisoners. His eyes even begin welling with tears as his lip starts quivering!
Suko being Forced to Watch as his caretaker, and presumably mother, is thrown to her death into a pool of lava by the Skar King for disobeying him.
Kong at seeing this finally loses what little restraint he had and attacks Skar King. Those who have read the supplementary comic Skull Island: Birth of Kong know that the day Kong himself was born was the day he was Forced to Watch his parents gets massacred by the Skullcrawlers. Witnessing this must have brought back a huge surge of trauma for Kong and to make it worse it’s one of his own kind who is doing it!
Shimo is a Woobie, Destroyer of Worlds: despite her immense power and capacity to bring about another ice age, she is ultimately just a Non-Malicious Monster kept enslaved by the Skar King and tortured into submission.
One moment that's particularly sad is when Godzilla and Kong have Skar King dead to rights, Shimo can't seem to comprehend the fact her tormentor is finally going to be gone and looks so uncertain.
Imagine Kong spending all his life searching for more like him, and finally succeed... only to find that they want him dead. The first other apes he meets attacks him right away and he's forced to fight them off, even sending one to his death. Over the course of the film, he's forced to kill at least eight of his bretheren (the one he kicks off the cliff, six of the guys chasing him using his traps, and Skar King), even though he was desperately searching for such apes no less than a few days (hours?) ago. Fortunately, the antagonistic apes are the minority, and these killings ultimately lead to the rest being freed.
A bit of Alas, Poor Villain, but Scylla's death by Godzilla's hand could count, as she was formerly one of the titans who bowed to Godzilla and actually was beneficial to the environment by slowing the melting of the ice caps.
Despite living amongst modern civilization for some time, poor Jia is having trouble acclimating to her environment and feels she doesn't belong anywhere, especially at her new school. Meanwhile, her teacher isn't exactly helping her feel at home, dismissing much of Andrews' concerns about her and chalking it up to her as being one amongst many of their culturally displaced students.
Ilene Andrews: I'm sorry, she's just still adjusting to our world. Teacher: I understand that, but we have a number of students who are culturally displaced. Ilene Andrews: Sure, but her culture is not "displaced", she is her culture. She is the last living member of the Iwi Tribe.
